Test ranges and other organizations often collect and distribute telemetry data in serial streams of data bits that are clocked and distributed in real-time at about 10 Mbits per second (or more). In some cases, when telemetry data are received at a ground station, the radio frequency (RF) receiver typically converts the data signal back to a serial digital stream and a bit synchronizer regenerates the clock signal to facilitate data distribution by keeping the data stream synchronized. In other cases, the serial data and clock are sent serially over an optical fiber or an electrical cable.
There are three main factors that can adversely influence telemetry data acquisition. The three main factors include third party equipment (TPE), environmental factors (e.g., temperature and electromagnetic interference (EMI)), and power/grounding quality. With respect to each of these three main factors, there are additional considerations that affect telemetry data acquisition.
The TPE and cables may be provided between the clock and data signals generated by the test range and the point at which the user has access to the clock and data signals. The TPE may include distribution amplifiers, multiplexors, demultiplexors, derandomizers, decryptors, and cables. The TPE may introduce distortions into the clock and data signals, and the distortions may manifest themselves as timing skew between the clock and data signals and/or as polarity changes and/or as signal rise time changes that adversely affect the ability to know when to sample the data and how best to correctly record the data.
Environmental factors may impact the equipment when electromagnetic interference (EMI) is encountered or as temperatures change. Environmental temperature changes, or temperature changes relative to the equipment itself (e.g., as the equipment heats up) can each negatively affect telemetry data acquisition. In this regard, various operational parameters that are applicable at startup may no longer be applicable as temperature changes begin to take effect or as nearby equipment generates EMI.
The last main factor is power/grounding quality. Power/grounding quality is descriptive of the reliability and stability of the power source and the equipment grounds. Untimely power glitches, common-mode ground voltage differences, or random loss of power, can also interrupt acquisition and degrade data reliability. Thus, any downstream telemetry acquisition system must be capable of compensating for and correcting for the distortions mentioned above.
The cost and complexity of systems for gathering telemetry data is generally high. Moreover, especially in light of the challenges discussed above, gathering of telemetry data typically requires a skilled and experienced operator to properly set up the complex equipment and to ensure that the equipment is tested and then maintained in good working order as the data gathering is commenced and environmental or other conditions change. The complex systems that are generally used in this area also commonly require proprietary software that can be buggy and create reliance on bug fixes, patches and software updates. To address some of these drawbacks, solutions have been sought to minimize acquisition time and maximize the amount of recoverable data by improving acquisition technologies. The data systems described herein are capable of being used as generic waveform recorders. They also may be configured to obviate the need for best source selectors and to provide optimal telemetry processing and recording when multiple telemetry signals of differing quality are available.